1. Field of the Invention
The present invention relates to apparatus and a method for the application of topical negative pressure (TNP) therapy to wounds. In particular, but not exclusively, the present invention relates to a method and apparatus for determining status such as a fullness associated with a canister in a TNP system.
2. Background of the Invention
There is much prior art available relating to the provision of apparatus and methods of use thereof for the application of TNP therapy to wounds together with other therapeutic processes intended to enhance the effects of the TNP therapy. Examples of such prior art include those listed and briefly described below.
TNP therapy assists in the closure and healing of wounds by reducing tissue oedema; encouraging blood flow and granulation of tissue; removing excess exudates and may reduce bacterial load and thus, infection to the wound. Furthermore, TNP therapy permits less outside disturbance of the wound and promotes more rapid healing.
In our co-pending International patent application, WO 2004/037334, apparatus, a wound dressing and a method for aspirating, irrigating and cleansing wounds are described. In very general terms, this invention describes the treatment of a wound by the application of topical negative pressure (TNP) therapy for aspirating the wound together with the further provision of additional fluid for irrigating and/or cleansing the wound, which fluid, comprising both wound exudates and irrigation fluid, is then drawn off by the aspiration means and circulated through means for separating the beneficial materials therein from deleterious materials. The materials which are beneficial to wound healing are recirculated through the wound dressing and those materials deleterious to wound healing are discarded to a waste collection bag or vessel.
In our co-pending International patent application, WO 2005/04670, apparatus, a wound dressing and a method for cleansing a wound using aspiration, irrigation and cleansing wounds are described. Again, in very general terms, the invention described in this document utilises similar apparatus to that in WO 2004/037334 with regard to the aspiration, irrigation and cleansing of the wound, however, it further includes the important additional step of providing heating means to control the temperature of that beneficial material being returned to the wound site/dressing so that it is at an optimum temperature, for example, to have the most efficacious therapeutic effect on the wound.
In our co-pending International patent application, WO 2005/105180, apparatus and a method for the aspiration, irrigation and/or cleansing of wounds are described. Again, in very general terms, this document describes similar apparatus to the two previously mentioned documents hereinabove but with the additional step of providing means for the supply and application of physiologically active agents to the wound site/dressing to promote wound healing.
The content of the above references is included herein by reference.
However, the above apparatus and methods are generally only applicable to a patient when hospitalized as the apparatus is complex, needing people having specialist knowledge in how to operate and maintain the apparatus, and also relatively heavy and bulky, not being adapted for easy mobility outside of a hospital environment by a patient, for example.
Some patients having relatively less severe wounds which do not require continuous hospitalization, for example, but whom nevertheless would benefit from the prolonged application of TNP therapy, could be treated at home or at work subject to the availability of an easily portable and maintainable TNP therapy apparatus.
GB-A-2 307 180 describes a portable TNP therapy unit which may be carried by a patient clipped to belt or harness. It will however be appreciated that from time to time errors may occur during operation of the TNP therapy unit. One particular problem which can occur is that when a canister utilised to filter and store waste product becomes full correct operation of the TNP system can be impeded. With current devices two pressure sensors are required on each side of a canister to detect such an event. A change in measured pressure between the two sensors implies a blocked canister filter which further implies a full canister. It will be appreciated that the use of two such sensors is both expensive and prone to error and requires complex processing elements to determine when a canister is full.